Which comes first, happiness or money? Much scholarly head tapping has been devoted to examining whether richer people are happier and if so, how much richer? Nobel prize-winners have even looked into it. But a new study suggests that the question could perhaps be looked at the other way around. Happier teenagers, this study suggests, grow up to be richer adults.

The study, which appeared recently in the Proceedings of the National Association of Sciences, looked at thousands of teenagers and found that those who felt better about life as young adults tended to have higher incomes by the time they turned 29. Their happiness was measured on a scale of 1 to 5. Those who were happiest earned an average of $8,000 more than those who were the most despondent.

The researchers, from University College London and the University of Warwick, used American data from the 10,000 strong survey known as Add Health, and say that their findings held firm even when factoring other variables that also tend to influence both happiness and wealth, such as IQ, education level, self esteem and even height. Very gloomy teens, no matter how tall or smart they were, earned 10% less than their peers, while more exuberant ones earned up to 30% more.

When the researchers repeated the study with sibling pairs—youngsters with the same parents and socio-economic backgrounds—the happier ones continued to earn bigger paychecks (which probably didn’t help the mood of the already more gloomy ones.) It may be that happier teenagers have an easier time getting through school, college and a job interview, partly because they feel better about life generally. It may also be true that happier people find it easier to make friends, who are often the key to homework help or networking. Let’s face it, Winnie the Pooh is more popular than Eeyore. And Big Bird is more popular than Oscar the Grouch.

The big question here is that if it really is true that happier kids end up being wealthier kids, where does that leave parents vis-a-vis homework? Make the kids do it, even though it makes them miserable, or allow it to slide, even though that will hurt their grades? Studies do show, after all, that more education leads to better paying jobs. Which, taken together with the current study results, only suggests a trickier solution: that it’s probably best to find a way to help children gain more satisfaction from doing schoolwork. “These findings show that the emotional well-being of children and adolescents is key to their future success,” one of the report’s authors, Jan-Emmanuel De Neve writes. “Yet another reason to ensure we create emotionally healthy home environments.”